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Using virOnce for global initialization is desirable since it

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ensures that initialization will always take place when it is
needed, and guarantees it only occurs once. The problem is that
the code to setup a global initializer with proper error
propagation is tedious. This introduces VIR_ONCE_GLOBAL_INIT
macro to simplify this.

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
This commit is contained in:
Daniel P. Berrange 2012-07-20 15:03:39 +01:00
parent c7af2c125e
commit 9b13660ee7
1 changed files with 49 additions and 0 deletions
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49
src/util/threads.h
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@ -114,4 +114,53 @@ int virThreadLocalSet(virThreadLocalPtr l, void*) ATTRIBUTE_RETURN_CHECK;
# error "Either pthreads or Win32 threads are required"
# endif
/**
* VIR_ONCE_GLOBAL_INIT:
* classname: base classname
*
* This macro simplifies the setup of a one-time only
* global file initializer.
*
* Assuming a class called "virMyObject", and a method
* implemented like:
*
* int virMyObjectOnceInit(void) {
* ...do init tasks...
* }
*
* Then invoking the macro:
*
* VIR_ONCE_GLOBAL_INIT(virMyObject)
*
* Will create a method
*
* int virMyObjectInitialize(void);
*
* Which will ensure that 'virMyObjectOnceInit' is
* guaranteed to be invoked exactly once.
*/
# define VIR_ONCE_GLOBAL_INIT(classname) \
static virOnceControl classname ## OnceControl = VIR_ONCE_CONTROL_INITIALIZER; \
static virErrorPtr classname ## OnceError = NULL; \
\
static void classname ## Once(void) \
{ \
if (classname ## OnceInit() < 0) \
classname ## OnceError = virSaveLastError(); \
} \
\
static int classname ## Initialize(void) \
{ \
if (virOnce(&classname ## OnceControl, classname ## Once) < 0) \
return -1; \
\
if (classname ## OnceError) { \
virSetError(classname ## OnceError); \
return -1; \
} \
\
return 0; \
}
#endif